One tube radioreceiver



W. R. KOCH ONE TUBE RADI ORECEIVER June 25, 1935.

Filed Jan. 27, 1934 v V I/vvE/vme:

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Patented June 25, 1935 g I V UNITED STATES! PATIENT OFFICE ONE TUBE RADIOREOEIVER Winfield K. Koch, Camden, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 27, 1934, Serial No. 708,539 8 Claims. (o1. 250-20) My invention relates to radio receivers and para triode portions of this tube. The triode portion ticularly to improvements in receivers of the type alsocomprisesits own anode 9 and control grid 8. which is suitable for use in an airplane or other My receiving circuit is adapted to respond to vehicle. For such use it is essential that limitaspace signals as collected by any suitable antenna 5. tions be imposed upon the weight and bulk of the 2|. A response to'the signals may be had through r ceiver, theradio frequency transformer 22 and the tuned Where weight and portability are of no concircuit Whichincludes the tuning condenser 23. sequence, sensitivity, selectivity, volume of sound The signals are then transferred through the reproduction and other desirable features may blocking condenser 24 to the control grid 4. The

lO easily be had in a radio receiver by adding the radio frequency signals are first amplified through necessary tubes and stages of amplification and the action of the pentode portion of the tube l, by providing a sufficiently high powered source of the output circuit of which includes the primary energy; but where space and weight become imwinding of aradio frequency transformer l2. The portant considerations, numerous difficulties are secondary winding of this transformer is tunable encountered in designing such a receiver as would by means of a variable condenser l4. A common 15' be suitable for receiving beacon signals, weather control may be provided-for the two tuning conreports and other communications required b densers 23 and M. v s aviators. r The radio frequency signals are then trans- Accordingly, my invention has forits object ferred through the blocking condenser H to the to provide a radio receiver which is small, light, control grid 8 in'the triode portion of the tube. 0

simple and rugged in construction. 7 I This control grid is provided with a grid leak l 0 A further object of my invention is to provide whereby the triode portion of the tube acts'as a a radio receiver which requires only one tube and detector. The output circuit connecting with which, therefore, can be operated from the lightthe anode 9 includes a regenerative coil l3.which 25 ing circuit of an airplane, if desired, or from afew is coupled with the transformer [2. Energy is 25 dry cells or other source of power which would supplied by the battery or other source .32 for imbe of minimum weight. I 7 pressing suitable potentials upon the various Another object of my invention is to provide a electrodes, both of the pentode portion and. of the radio receiver of the, type indicated above in triode portion of the tube. As'shown in the diawhich a single electron tube may be utilized to gram, the screen grid5may have impressed there- 30 obtain a high degree of gain in the amplification on the highest potential while the potential of of signals. I V 1 the anode"! may be made only slightly lower due The novel features that I consider characterto the comparatively low voltage drop through istic of my invention are set forthwith parthe phones 3| and the primary of the radio freticularity in the appended claims. The invention quency transformer l2. The voltage applied t6 35 itself, however, both as to its organization and the anode 9 ismade variable by including in the its method of operation together with additional output circuit thereof a potentiometer l5 having objects and advantages thereof will best be undera movable tap l6 associated therewith. This tap stood from the, following description of a specific is connected to the primary 26 of an audio fre- 40 embodiment when read in connection with the quency transformer 25. As showninthe diagram, 40 accompanying drawing in which the single figure when the tap is moved to the right the portion thereof is a circuit diagram showing the essential of thepotentiometer I5 which is shunted by the features of my one-tube receiver. primary winding 26 becomes diminished. Since Referring now to the drawing, Ishow an electhe primary winding 26 has a comparatively low tron tube l which is preferably of the combined ohmic resistance, it will be seen that the voltage 45 pentode-triode type. Such a tube is at present impressed upon the anode 9 through the regeneraavailable on the market and is known as an RCA tive coil l3 may be increased by moving the tap 6F? tube. The tube is characterized as havinga Hi to the left (as shown in the diagram) whereby pentode portion comprising a heatingelement 2, a more of the resistance in the potentiometer I5 is cathode 3, an anode l and three grids, one of bypassed. Furthermore, the radio frequency curwhich is a control grid 4, the second a screen grid rents through the regenerative coil [3 may be 5 and the third a suppressor grid 6 connecting more or less impeded by adjustingthe setting of with the cathode 3. the tap l6, since these currents arefed through The aforementioned cathode 3 and heatingelethe left hand portion of the potentiometer l5 to 1 ment' 2 are common to both the pentode and the tap l6 and thence throughgthe bypass condenser I! to ground. The adjustment of the potentiometer serves, therefore, to control the amount of regeneration set up by the coil 13.

The potentiometer has, however, a dual purpose. Its adjustment provides a secondary effect; namely, that of increasing or decreasing the portion of the signalling energy which, after rectification, may be impressed through a primary .26. of the audio frequency transformer 25 so as to step up the voltage of the audio signals and reflex the same from the secondary 21 of this transformer upon the control grid 4 of the pentode portion of the tube.

pedance to audio frequency currents. but a high impedance to radio frequency currents. In place of the resistor 28 a radio frequency choke might be used, although, for" economy of cost and space the resistor appears to be preferable; It will be noted at this point that the blocking condenser 24 is of such capacitance that it serves to prevent the dissipation of the refiexed' audio frequency signals back to ground through the 7 low resistance secondary of the radiofrequency transformer 22." r A I i Following out further the action of the audio frequency signals as impressed upon the control grid 4, it will be seen that they are a'mplified through the pentode portion of the tube, the output circuit of which leads to the' phones or other sound reproducing device 3|.

The remaining features of my improvedand simplified one-tube receiving circuit may be well understood by those skilled in'theart. For the purpose of: completeness of the description, however, they are referred toas'follows: V

The bypass condenser Il may be interposed between the tap lfi'of the potentiometer andground inorder to afford. a freev path for radio'frequency components in the output'circuit of thelregenerative detector. Asimilari bypass condenser. 30 is provided across the terminalsof the sound reproducing device 3 If which would otherwiseafford ail-undesirably high impedance to radio frequency currents in the output circuit of the pentode portionofthetube. T

The resistor '29 may be used across the leads to the phones 3| so as to straighten" out the response, characteristic of the latter inrespect' to different audio frequencies. V. The resistor l9 provides a difference of potential between the cathode 3:and ground in' order to properly bias the pentode grid 4. It is, therefore, employed as the usual self-bias resistor in the cathode return lead 33. Thefixed' condenser I8 is of the order ofseveral'microfarads in order that the radio and audiofrequency components of the plate currents through each portion of the tube may be bypassed to ground withoutitransferring any voltages to the other portion of the tube. 1

It will beseen from-the above and will also be recognized by those skilled in the art that the circuit as herein described has many advantages.

The single tube itself isof a rugged type capable of withstanding the vibrations and shocks incident to the carrying of a radio receiver in an airplane or automobile. This tube also has its a This refiex circuit includes a re-; sistor 28 which serves as a relatively low im-- a low voltage battery, it will be seen that one of the principal objects of my invention is achieved in that it is suitable for operation by a power plant of minimum weight. Furthermore, simplification is achieved by the provision of a potentiometer which is so constituted that it serves. a dual purpose; namely, to control the regeneration and also the volume of audio frequency energytransferred'to the refiex circuit. I

In an embodiment of my invention which has been built, it was found that a sensitivity of better than 250 microvolts could be obtained.

'Altho ugh I' have disclosed herein certain specific means for accomplishing the objects of my invention, these are given merely by way of example and are not'to be construed as limitations tothe scope of my invention. Other modifications will suggest themselves to those skilled in the. art. -My invention, therefore, is not to be limited except insofar as is necessitated by the prior art and by the spirit of the appendedclaims. I claim as my-invention: I

1. In a: radio receiver, a pentode-triode tube,

meansincluding the pentode-electrodes of said tube for amplifying radio frequency signals,

means including a tuned circuit to which the radio frequency output-fromthe pentode elec trodes of said tube islcoupled' for impressing signals to be detected upon the triode electrodes of said tube, an-output circuit for said triodeelec trodes regeneratively coupled to said tuned circuit, a potentiometer in said. output circuit, an

audio ifrequency transformer the primary of which connects between one end of said'potentiing its primary connected inshunt with a variable portion of said potentiometer'and its secondary connected from ground through a suitable radio.

frequency impedance tothe input side of said radio frequency amplification means, means'ineluding an audio frequency amplifier havingele ments thereof in common'with those of theradio frequency amplification means whereby a desired gain in audio frequency signal strength may be obtained, a sound reproducing unit responsive to audio frequency signals as delivered by said audio frequency amplification means and: means including an adjusting. member acting. solely upon said potentiometer to vary the degree of regeneration and simultaneously to control the voltage drop across theprimary of said audio. frequency transformer for. effecting a desiredvolume of signal response in said sound reproducing unit. 3. A device in accordancewith claim Z-further characterized in that a pentodetriodeelectron tube is provided in which the electrodes of the pentode portion are included in the radio frequency amplification means and also in the audio frequency amplification means, while the electrodes of the triode portion constitute a detector.

4 ..In a radio receiver, a singleelectric discharge tube having input and output electrodes thereof common to the functions of amplifying both radio frequency and audio frequency signals, means including additional electrodes of said tube connected on the input side with a resonant circuit and on the output side with a regenerative coil and thence through a potentiometer to a source of direct current for detecting and amplifying said signals, an audio frequency transformer, and means including an adjustable tap on said potentiometer for bypassing audio frequency signals in varying degree around a portion of said potentiometer and through said transformer, said means serving further for simultaneously controlling both the impedance path for radio frequency currents through said regenerative coil and also the direct current potential applied to one of said additional electrodes, specifically the anode thereof.

5.' In a radio receiver, a thermionic device having at least two output circuits and at least two input circuits, one input circuit for each output circuit, means for reflexing signal-representative potentials from one of said output circuits to the input circuit corresponding to the other of said output circuits and unitary means for simultaneously controlling the amplitude of the said potentials in the output circuit from which they are derived and the amplitude of the derived potentials reflexed into the input circuit.

6. In a radio receiver, an electron tube having a first set of input and output circuits and a sec ond set of input and output circuits, radio and audio frequency amplification means constituted by the first set, regenerative signal detection means constituted by the second set, coupling means for reflexing signal representative potentials from the output circuit of the second set to the input circuit of the first set, and means constituted solely by an adjustable potentiometer for controlling the amplitudes of the radio frequency and audio frequency components of the potentials in the input and output circuits of the second set while simultaneously controlling the amplitude of the derived audio frequency potentials reflexed into the input circuit of the first set.

7. In a radio receiver, two stages of amplification, one stage of regenerative demodulation, coupling means for impressing modulated potentials derived from the first stage of amplificationupon said stage of demodulation, coupling means for impressing demodulated signal-representative potentials upon the second stage of amplification, and means comprising an adjustable potentiometer for controlling the amount of regeneration while simultaneously controlling the amplitudes of the signal-representative potentials both in the stage of demodulation and in the second stage of amplification.

8. A device in accordance with claim 7 wherein the potentiometer is so connected between the stages that its adjustment one way results in a diminution of amplitudes both of the directcurrent component and of thealternating current components in the stage of demodulation, and its adjustment the other way results in an increment of potential drop of the signal-representative potentials impressed upon the'coupling means feeding to the second stage of amplification.

WINFIELD R. KOCH. 

